Electrocardiogram

Electrocardiogram

An Electrocardiogram (ECG) is a recording of the electrical activity in the heart. Doctors can analyse multiple different components of the ECG to gain information about heart rate and rhythm, and to look for the presence of conditions affecting the heart.

How the Test is Performed

An ECG is a relatively simple test which involves sticking about ten small electrodes on the chest and attaching them to a machine at the bedside. The machine analyses the heart’s electrical signals, picked up through the electrodes on the skin surface. It is a completely painless test but obviously requires temporary exposure of the chest, to allow placement of the leads. The actual reading takes about one minute and a printout with 12 waveforms is produced either at the machine itself, or at a nearby printer. A doctor or experienced and specialised nurse reads and interprets the ECG. Sometimes they will seek additional help from a more senior doctor or a cardiologist – even at a distance via fax. Occasionally the ECG is formally reported by a cardiologist – this is more likely in the routine or non-urgent situation.

Medical Conditions and Symptoms

An Electrocardiogram (ECG) may be ordered as a routine test, for example before an operation to assess the electrical function of the heart, or as an urgent test in the setting of chest pain or other cardiovascular symptoms (such as shortness of breath or palpitations).

Test Results Explained

The Electrocardiogram (ECG) is a very confusing array of squiggles and waveforms, to the uninitiated. There is a large amount of information conveyed by the ECG, as each separate bump or wave can be assessed for size, shape, and distance from other bumps on the ECG. It can show abnormalities of heart rate, rhythm, axis (the relative dominance of the left or right side of the heart), and conduction of impulses through the heart. The ECG can also show the presence of damage to the heart muscle, as in a heart attack, myocarditis, or pericarditis. It is also used to diagnose angina or an acute coronary syndrome, where inadequate blood supply to the heart muscle manifests as a strain on the heart (myocardial ischaemia).